Robust beam switch scheduling

ABSTRACT

Systems and methods are described for robust scheduling of beam switching patterns in satellite communications systems. Embodiments operate in context of a hub-spoke satellite communications architecture having a number of gateway terminals servicing large numbers of user terminals over a number of spot beams. The satellite includes switching subsystems that distribute capacity to the user beams from multiple of the gateway terminals in a shared manner according to a beam group switching pattern. The beam group switching pattern is robustly formulated to continue distributing capacity during gateway outages (e.g., when one or two gateway terminals are temporarily non-operational due to rain fade, equipment failure, etc.). For example, the beam group switching pattern can be formulated to minimize worst-case degradation of capacity across user beams, to prioritize certain beams or beam groups, etc.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/443,356, filed on Feb. 27, 2017, which is a continuation ofU.S. patent application Ser. No. 14/567,854, filed Dec. 11, 2014, issuedas U.S. Pat. No. 9,621,257 on Apr. 11, 2017, which is a continuation ofInternational Patent Application No. PCT/US13/44153, filed Jun. 4, 2013,which claims the benefit of priority to U.S. Provisional PatentApplication No. 61/791,059, filed Mar. 15, 2013, U.S. Provisional PatentApplication No. 61/658,269, filed Jun. 11, 2012, and U.S. ProvisionalPatent Application No. 61/658,273, filed Jun. 11, 2012, the entirecontents of each of which are incorporated by reference herein for allpurposes.

FIELD

Embodiments relate generally to satellite communications systems, and,more particularly, to robust scheduling of beam switching patterns insatellite communications systems.

BACKGROUND

A hub-spoke satellite communications system typically includes aconstellation of one or more satellites that links gateway terminalswith user terminals. The gateway terminals provide an interface with anetwork such as the Internet or a public switched telephone network.Each gateway terminal typically services a number of user terminalslocated in one or more spot beams. Gateway terminals are subject toservice interruptions due to weather, maintenance, disasters, etc. Atsuch times, the affected gateway terminals may not be able to providefull capacity to the user terminals that they serve.

BRIEF SUMMARY

Among other things, systems and methods are described for robustscheduling of beam switching patterns in satellite communicationssystems.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is described in conjunction with the appendedfigures:

FIG. 1 shows a block diagram of an embodiment of a hub-spoke satellitecommunications system, according to various embodiments;

FIG. 2 shows a block diagram of an illustrative satellite communicationssystem having gateway terminals in forward-link communication with userterminals via a satellite, according to various embodiments;

FIG. 3 shows a block diagram of an illustrative satellite configurationhaving multiple beam group switching subsystems associated with multiplebeam groups, according to various embodiments;

FIG. 4 shows control and storage components used to control operation ofthe switching subsystems in some embodiments;

FIGS. 5A-5D show a non-robust beam group switching pattern in normal andsingle-gateway outage conditions, respectively, for the sake of context;

FIGS. 6A and 6B show an illustrative robust beam group switching patternand an associated illustrative system in a normal condition;

FIGS. 6C-6E show an illustrative robust beam group switching pattern andan associated illustrative system in a condition during which thegateway terminal associated with beam group 1 is non-operational;

FIGS. 7A-7D show four configurations of an illustrative system forsourcing forward-link capacity to a user beam in a shared manner amongfour gateway terminals;

FIGS. 8A-8D show four configurations of an illustrative system forsinking return-link capacity from a user beam in a shared manner amongfour gateway terminals;

FIG. 9 shows a flow diagram of an illustrative method for robust sharingof gateway resources between gateway terminals and user terminals overfixed location beams, according to various embodiments;

FIG. 10 shows a flow diagram of an illustrative method for distributingcapacity to each output user feed from multiple of the gateway inputfeeds in a shared manner; and

FIGS. 11A and 11B show flow diagrams of another illustrative method forrobust sharing of gateway resources between gateway terminals and userterminals over fixed location beams in forward-link and return-linkconfigurations, respectively, according to various embodiments.

In the appended figures, similar components and/or features can have thesame reference label. Further, various components of the same type canbe distinguished by following the reference label by a second label thatdistinguishes among the similar components. If only the first referencelabel is used in the specification, the description is applicable to anyone of the similar components having the same first reference labelirrespective of the second reference label.

DETAILED DESCRIPTION

In a hub-spoke satellite communications system, each of a number ofgateway terminals typically services a large number of user terminalsvia multiple user feeds supported by multiple spot beams. When anygateway terminals experience service interruptions (e.g., due toweather, maintenance, disasters, etc.), the affected gateway terminalsoften cannot provide full capacity to the user terminals that theyserve. In traditional implementations, where each user terminal istypically serviced by a particular one of the gateway terminals, largegroups of user terminals can lose all their connectivity when theirrespective servicing gateway terminal goes down.

Embodiments provide novel techniques for scheduling of beam switchingpatterns to distribute capacity to user beams from multiple gatewayterminals in a shared manner. For example, multiple gateway terminalsshare sourcing of capacity for any given user terminal, so that theimpacts of limited gateway outages on user terminal connectivity can bereduced. The beam group switching patterns can be robustly formulated tomaintain at least a minimum aggregate threshold of capacity acrossmultiple user beams during limited gateway outages. In someimplementations, beam group switching patterns are formulated tominimize worst-case degradation of capacity across user beams, toprioritize certain beams or beam groups, or to achieve other goals.

Turning first to FIG. 1, a block diagram is shown of an embodiment of ahub-spoke satellite communications system 100, according to variousembodiments. The satellite communications system 100 includes a groundsegment network 150 in communication with multiple user terminals 110via a space segment (one or more satellites 105). The ground segmentnetwork 150 can include any number of gateway terminals 165, core nodes170, network operations centers (NOCs), satellite and gateway terminalcommand centers, and the like. The term “ground” is used herein togenerally include portions of the network not in “space.” For example,embodiments of the ground terminals can include mobile aircraftterminals and the like. Further, while user terminals 110 aretechnically part of the ground segment of the satellite communicationssystem 100, they are discussed separately for the sake of clarity.Though not shown, each user terminal 110 can be connected to variousconsumer premises equipment (CPE) such as computers, local area networks(e.g., including a hub or router), Internet appliances, wirelessnetworks, and the like. In some implementations, user terminals 110include fixed and mobile user terminals 110.

In a hub-spoke architecture, all communications pass through at leastone gateway terminal 165. For example, a communication from a first userterminal 110 to a second user terminal can pass from the first userterminal 110 to a gateway 165 via the satellite 105, and from thegateway 165 to the second user terminal 110 via the satellite 105.Accordingly, communications can be considered as coming from a gatewayterminal 165 or going to a gateway terminal 165. Communications comingfrom one or more gateway terminals 165 are referred to herein as“forward” or “forward-link” communications, and communications going toone or more gateway terminals (e.g., from user terminals 110) arereferred to herein as “return” or “return-link” communications.Communications from the ground (e.g., gateway terminals 165 and userterminals 110) to space (e.g., the satellite 105) are referred to hereinas “uplink” communications, and communications to the ground from spaceare referred to herein as “downlink” communications. In that parlance,the gateway terminals 165 can communicate to the satellite 105 over aforward uplink channel 172 via one or more gateway antennas 145 and canreceive communications from the satellite 105 over a return downlinkchannel 174 via the one or more gateway antennas 145; and the userterminals 110 can communicate to the satellite 105 over a return uplinkchannel 178 via their user antennas 115 and can receive communicationsfrom the satellite 105 over a forward downlink channel 176 via theiruser antennas 115.

The gateway terminal 165 is sometimes referred to as a hub or groundstation. While the gateway terminals 165 are typically in fixedlocations, some implementations can include mobile gateways. The gatewayterminal 165 can also schedule traffic to the user terminals 110.Alternatively, scheduling can be performed in other parts of thesatellite communications system 100 (e.g., at one or more core nodes170). Scheduling information can be communicated through a terrestrialnetwork, a satellite command link, the communications system 100, etc.in any suitable manner. As described herein, certain schedulinginformation is used to robustly distribute capacity to user terminals110 in a shared manner from multiple gateway terminals 165. Schedulingpatterns and/or other information relating to this type of schedulingcan be maintained and/or generated at the satellite 105, the gatewayterminals 165, the core nodes 170, etc.

The ground segment network 150 can distribute ground segmentfunctionality among various components. For example, geographicallydistributed core nodes 170 are in communication with the Internet 175(and/or other public and/or private networks) and with each other via ahigh-speed, high-throughput, high-reliability terrestrial backbonenetwork. The core nodes 170 have enhanced routing, queuing, scheduling,and/or other functionality. Each gateway terminal 165 is incommunication with one or more core nodes 170 (e.g., redundantly).Groups of user terminals 110 are serviced by multiple gateway terminals165 via the satellite 105 and user beams. Accordingly, return-linkcommunications from a user terminal destined for the Internet can becommunicated from the user terminal to the satellite 105 via a userbeam, from the satellite 105 to multiple gateway terminals 165 viarespective gateway beams, from the gateway terminals 165 to one or morecore nodes 170 via the ground segment network 150, and from the one ormore core nodes 170 to the Internet 175 via a backbone network.Similarly, forward-link communications to a user terminal from theInternet can arrive at a core node 170 via the backbone network, bedistributed to one or more gateway terminals 165 via the ground segmentnetwork 150, and be communicated from the one or more gateway terminalsto the user terminal 110 via the satellite 105.

Though illustrated as the Internet 175, the ground segment network 150can be in communication with any suitable type of network, for example,an IP network, an intranet, a wide-area network (WAN), a local-areanetwork (LAN), a virtual private network (VPN), a public switchedtelephone network (PSTN), a public land mobile network, and the like.The network can include various types of connections, like wired,wireless, optical or other types of links. The network can also connectground segment network 150 components to each other and/or with otherground segment networks 150 (e.g., in communication with othersatellites 105).

Each gateway antenna 145 and user antenna 115 can include a reflectorwith high directivity in the direction of the satellite 105 and lowdirectivity in other directions. The antennas can be implemented in avariety of configurations and can include features, such as highisolation between orthogonal polarizations, high efficiency in theoperational frequency bands, low noise, and the like. In one embodiment,a user antenna 115 and a user terminal 110 together comprise a verysmall aperture terminal (VSAT) with the antenna 115 having a suitablesize and having a suitable power amplifier. In other embodiments, avariety of other types of antennas 115 are used to communicate with thesatellite 105.

Each antenna is configured to communicate with the satellite 105 via aspot beam (e.g., a fixed location user beam or gateway beam). Forexample, each antenna points at the satellite 105 and is tuned to aparticular carrier (and/or polarization, etc.). The satellite 105 caninclude one or more fixed-focus (e.g., gimbaled) directional antennasfor reception and transmission of signals. For example, a directionalantenna includes a fixed reflector with one or more feed horns for eachspot beam. Typically, the satellite communications system 100 haslimited frequency spectrum available for communications. The varioususer beams and gateway beams can use the same, overlapping, or differentfrequencies, polarizations, etc. In some embodiments, some or allgateway terminals 165 are located away from the user terminals 110,which can facilitate frequency re-use. In other embodiments, some userterminals 110 are located near some or all gateway terminals 165. Incertain implementations, certain user terminals 110 can communicate withthe satellite 105 via certain gateway beams.

Contours of a spot beam can be determined in part by the particularantenna design and can depend on factors, such as location of feed hornrelative to a reflector, size of the reflector, type of feed horn, etc.Each spot beam's contour on the earth can generally have a conical shape(e.g., circular or elliptical), illuminating a spot beam coverage areafor both transmit and receive operations. A spot beam can illuminateterminals that are on or above the earth surface (e.g., airborne userterminals, etc.). In some embodiments, directional antennas are used toform fixed location spot beams (or spot beams that are associated withsubstantially the same spot beam coverage area over time). Certainembodiments of the satellite 105 operate in a multiple spot-beam mode,receiving and transmitting a number of signals in different spot beams.Each individual spot beam can serve a gateway terminal 165, a number ofuser terminals 110, both a gateway terminal 165 and a number of userterminals 110, etc. Each spot beam can use a single carrier (i.e., onecarrier frequency), a contiguous frequency range (i.e., one or morecarrier frequencies), or a number of frequency ranges (with one or morecarrier frequencies in each frequency range). Some embodiments of thesatellite 105 are non-regenerative, such that signal manipulation by thesatellite 105 provides functions, such as frequency translation,polarization conversion, filtering, amplification, and the like, whileomitting data demodulation and/or modulation and error correctiondecoding and/or encoding.

While a spot beam can refer to a particular coverage area (e.g., anelliptical are) serviced by a transponder of the satellite 105, the term“beam” as used herein generally includes a communications link or set ofcommunications links serviced via a spot beam. For example, an “inputbeam” can be used by the satellite 105 to receive uplink traffic fromeither a user terminal 110 (return-link traffic) or a gateway terminal165 (forward-link traffic) in a respective spot beam, and an “outputbeam” can be used by the satellite 105 to transmit downlink traffic toeither a user terminal 110 (forward-link traffic) or a gateway terminal165 (return-link traffic) in a respective spot beam. In someembodiments, each input beam and each output beam is serviced by a feedof the satellite 105. For example, a particular user feed is configuredto receive return-channel uplink traffic from user terminals via aninput beam associated with a spot beam that provides coverage to thoseuser terminals.

FIG. 2 shows a block diagram of an illustrative satellite communicationssystem 200 having terminals 205 in communication with each other via asatellite 105, according to various embodiments. The satellite 105includes input subsystems 210 and output subsystems 230 in communicationvia one or more beam group switching subsystems 250. Communications flowfrom the input subsystems 210 to the output subsystems 230 through theone or more beam group switching subsystems 250. Each input subsystem210 is associated with one or more input beams 215 (e.g., two, nine, orsome other number of beams), and each output subsystem 230 is associatedwith one or more output beams 240.

The terminals 205 can include gateway terminals and user terminals, andthe input beams 215 and/or output beams 240 can be designated as “userbeams,” gateway beams,” etc. In one implementation, user terminals in aparticular spot beam coverage area can communicate with the satellite105 via a user beam, and the user beam is actually a user input beam anda user output beam. For example, in a geographic region (e.g., a spotbeam coverage area), the user input beams communicate at a particularuplink frequency band (e.g., 27.5-30 Gigahertz), and the user outputbeams communicate at a particular downlink frequency band (e.g.,17.7-20.2 Gigahertz) to avoid interference between return-channel uplinkand forward-channel downlink traffic. In certain implementations, beamsdesignated for gateway use also service users located in the samecoverage area and are referred to as “gateway/user beams,” or “GW/U.” Insome implementations, gateway terminals and/or user terminals can havemultiple antennas, tuning components, and other functionality that cansupport communications over different beams and/or at differentfrequencies, polarizations, etc.

In certain implementations, different beams are associated withdifferent transmit and/or receive powers, different carrier frequencies,different polarizations, etc. For example, a particular spot beam canhave a fixed location and can support user uplink traffic, user downlinktraffic, gateway uplink traffic, and gateway downlink traffic, each atdifferent carrier/polarization combinations. In one implementation, anumber of gateway terminals 165 are geographically distributed, somenear user terminals 110 and some remote from user terminals 110. Thesatellite 105 supports a number of spot beams that together provide alarge coverage area for all the user terminals 110 and gateway terminals165. Different carrier frequencies, polarizations, and/or timing (e.g.,transmit and/or receive switching, as discussed below) can be used tomitigate interference between the beams and/or to facilitate frequencyreuse. Some embodiments group sets of beams (into “beam groups”) thathave particular characteristics. For example, a beam group can include anumber of beams that are geographically distributed but operate on thesame frequency bands (e.g., with the same or different respectivechannelizations).

According to some embodiments, each input subsystem 210 can sequentiallyswitch among its input beams 215 (e.g., according to an input beamswitching pattern) and/or each output subsystem 230 can sequentiallyswitch among its output beams 240 (e.g., according to an output beamswitching pattern). In other embodiments, some or all of the input beamsare communicatively coupled with an input of the beam group switchingsubsystem 250 (e.g., via one or more receive components, likeamplifiers, filters, etc.), and some or all of the output beams arecommunicatively coupled with an output of the beam group switchingsubsystem 250 (e.g., via one or more transmit components, likeamplifiers, filters, etc.). Embodiments of the beam group switchingsubsystem 250 can selectively couple some or all of the input subsystems210 with some or all of the output subsystems 230 according to a beamgroup switching pattern 252. In one embodiment, a switch matrix providesa full P×P non-blocking cross-connectivity (e.g., allowing Psimultaneous one-to-one connections between any permutation of the Pinputs and P outputs). For example, the beam group switching subsystem250 includes a matrix switch that can sequentially couple any inputsubsystem 210 with any output subsystem 230 according to the beam groupswitching pattern 252. Using the beam group switching subsystem 250(e.g., and input and/or output switching), forward-link traffic frommultiple gateway terminals received by the satellite 105 viacorresponding input beams 215 can be directed to any particular userterminal 110 via a corresponding output beam 240, and return-linktraffic from any particular user terminal received by the satellite 105via a corresponding input beam 215 can be directed to multiple gatewayterminals 110 via corresponding output beams 240. In another embodiment,a switch matrix provides less than a full P×P non-blockingcross-connectivity (e.g., the switch matrix allows inputs to connect tovarious subsets of the outputs, or subsets of inputs to connect withsubsets of outputs). In these and other ways, the capacity of eachoutput subsystem 230 can be sourced in a shared manner by any one ormore of the input subsystems 210.

In some embodiments, the beam group switching subsystem 250 sequentiallycouples the input subsystems 210 with the output subsystems in such away that distributes a first aggregate capacity to the output subsystems230 in a shared manner from P of the input subsystems 210 according tothe beam group switching pattern 252 when P gateway terminals 165associated with the P input subsystems 210 are operational. For example,the beam group switching subsystem 250 is an 8-by-8 switch matrix thatcan couple any of eight inputs (coupled with respective input subsystems210) with any of eight outputs (coupled with respective outputsubsystems 230). The beam group switching pattern 252 is configured todistribute a first capacity (e.g., a “full capacity”) from the eightinput subsystems 210 in a shared manner to the eight output subsystems230. The beam group switching pattern 252 is further configured todistribute a second capacity to the output subsystems 230 in a sharedmanner from fewer than eight input subsystems 210 (i.e., a remaining Qof the P input systems 210) according to the same beam group switchingpattern 252 when fewer than all of the associated gateway terminals 165are operational. For example, when one or two of the gateway terminals165 are temporarily non-operational (e.g., due to rain fade, temporaryequipment malfunction, etc.), the beam group switching pattern 252 isrobust enough to maintain at least a predetermined threshold aggregatecapacity for providing communications services to the user terminals 110via the output subsystems 230.

Some embodiments are configured to switch to one or more alternativerobust beam group switching patterns 252 in response to certainconditions. Typically, the robust beam group switching pattern 252 isconfigured to maintain adequate capacity across user beams with up to acertain extent of degradation in gateway capacity. For example, therobust beam group switching pattern 252 is designed to be a “robusttwo-out pattern” that maintains at least a minimum threshold amount ofcapacity when up to two gateway terminals 165 are non-operational.However, when any one gateway terminal 165 experiences a long-termoutage (e.g., equipment malfunction, etc.), when any two gatewayterminals 165 experience a long-term outage, or in any other suitablecondition, an alternate robust beam group switching pattern 252 is usedby the satellite 105 that is more optimized to the condition. In someimplementations, the alternate robust beam group switching pattern 252is received at the satellite 105 from a ground segment component (e.g.,a gateway terminal 165) in response to detecting the long-term outage.For example, gateway terminals 165 sense fade on loopback andcommunicate the condition to a core node, or a gateway terminal 165outage is otherwise detected by a core node, which has a number ofpre-stored alternative robust beam group switching patterns 252. Inresponse to the detection, the core node transmits an appropriate, newrobust beam group switching pattern 252 to the satellite 105. In otherimplementations, the alternative robust beam group switching patterns252 are stored at the satellite 105 and are switched in, as appropriate,upon detection of a long-term outage or similar condition. For example,the detection of the condition occurs in the ground segment, and anindication of the detection is communicated to the satellite 105.

The robustness of the beam group switching pattern 252 can be designedto facilitate certain goals. One such goal is to minimize (to apractical and/or desirable extent) worst-case (or maximum) capacitydegradation across the output beams 240 of the respective beam groups ofthe output subsystems 230 (sometimes referred to as “min-max”). Thissame goal can be alternatively considered as maximizing a minimumcapacity in case of limited gateway outages (e.g., the worst-casecapacity for which the robust beam group switching pattern 252 isdesigned is as good as possible). For the sake of illustration, with Pgateway terminals 165 normally sourcing capacity for the output beams240, the goal can be for the second aggregate capacity to approximateQ/P of the first aggregate capacity when only Q of the P gatewayterminals 165 are operational (e.g., seven eights of the full capacitywhen seven of eight gateway terminals 165 are operational). Typically,some spot beams receive less than the second capacity and othersreceived more than the second capacity, but the goal is to approximatean aggregate capacity of Q/P across a large number of beams.

Other beam group switching patterns 252 can be designed towards a goalof prioritizing certain user terminals 110 (or spot beams, beam groups,etc.). The prioritization can be for any suitable reason, for exampleaccording to different tiers of customers (e.g., enterprise versusresidential customers, etc.). In some implementations, traffic shapingand/or other techniques are used in conjunction with beam-level orbeam-group-level prioritization to further prioritize traffic for userterminals 110 or groups of user terminals 110. One illustrativeprioritization approach involves increasing gateway diversity forcertain beams or beam groups over others. For example, F of P gatewayterminals 165 are used to source capacity in a shared manner to higherpriority user beams, and G of the P gateway terminals 165 are used tosource capacity in a shared manner to higher priority user beams, whereF is greater than G. In this way, loss of service from any one gatewayterminal 165 is less likely to affect capacity of the user beams beingserviced by a greater diversity of gateway terminals 165.

Another illustrative prioritization approach exploits “high reliability”gateway terminals 165. In some implementations, a portion of the gatewayterminals 165 are configured to have appreciably higher reliability thanthe other gateway terminals 165, for example, by including in those highreliability gateway terminals 165 more capable or reliable components,more redundancy, larger antennas, etc. The beam group switching pattern252 can be designed to source capacity to higher reliability user beamsfrom high reliability gateway terminals 165. In one implementation, thehigh reliability gateway terminals 165 are grouped with the higherreliability user beams through one or more beam group switchingsubsystems 250, and other gateway terminals 165 are grouped with otheruser beams through one or more other beam group switching subsystems250. In another implementation, the beam group switching subsystem 250includes some high reliability gateway terminals 165 and regular gatewayterminals 165, and the beam group switching pattern 252 couples the highreliability gateway terminals 165 with the higher reliability user beamsmore of the time (e.g., exclusively, a higher proportion of eachpattern, etc.).

The satellite communications system 200 can use a framed hub-spoke,beam-switched pathway access protocol having time slots, such as aSatellite Switched Time-Division Multiple Access (SS/TDMA) scheme. Asused herein, a “slot” or “time slot” refers to a smallest time divisionfor switching according to the beam group switching pattern 252 (e.g.,and input and/or output beam switching patterns). A “frame” refers to aset of slots (e.g., of predetermined length). For example, a frame caninclude the number of slots defined by the beam group switching pattern252 and/or input and output beam switching patterns, so that any or allswitching patterns repeat once per frame. Each time slot can correspondto either forward-link or return-link traffic from a transmitting beamto a receiving beam.

During normal operation, continuous streams of frames are typically usedto facilitate communications. Multiple terminals can be serviced duringeach time slot using multiplexing and multiple access techniques (e.g.,Time-Division Multiplexing (TDM), Time-Division Multiple Access (TDMA),Frequency-Division Multiple Access (FDMA), Multi-Frequency Time-DivisionMultiple Access (MF-TDMA), Code-Division Multiple Access (CDMA), and thelike). For example, a forward-link time slot can be divided intomultiple “sub-slots” wherein transmissions to different user terminalsor groups of user terminals are made in each sub-slot. Similarly, areturn-link time slot may be divided into multiple sub-slots, which canbe reserved for network control or signaling information (e.g.,communication of scheduling information).

FIG. 3 shows a block diagram of an illustrative satellite configuration300 having multiple beam group switching subsystems 250 associated withmultiple beam groups 325, according to various embodiments. Thesatellite configuration 300 can represent an embodiment of satellite 105described herein. As in FIG. 2, each beam group switching subsystem 250has associated input subsystems 210 and output subsystems 230. In theillustrated embodiment, each input system 210 includes one or morereceive switches 330, and each output subsystem 230 includes one or moretransmit switches 340 that can facilitate switching between user and/orgateway feeds as described below. Designations, like “user beam,” “userfeed,” “gateway beam,” or “gateway feed” are included for added clarity,but are not intended to be limiting. For example, some implementationsallow user terminals 110 to communicate over gateway beams, and thecorresponding beams and feeds are designated generally as a “GW” “GW/U.”In some embodiments, some or all of the input subsystems 210 areimplemented without receive switches 330 and/or some or all of theoutput subsystems 230 are implemented without transmit switches 340. Incertain implementations, each feed is coupled with an input or outputport of a beam group switching subsystem 250, so that the beam groupswitching subsystem 250 can effectively couple input feeds with outputfeeds without additional beam switching.

Though not shown, the input systems 210 and/or output subsystems 230 canalso include any other supporting functionality, including, for example,amplifiers, converters, filters, etc. In one implementation, each inputsubsystem 210 includes a low-noise amplifier (LNA), and each outputsubsystem 230 includes a high-power amplifier (HPA) (e.g., a travelingwave tube amplifier (TWTA)). In some embodiments, the receive switches330 and/or transmit switches 340 are implemented as “fast” switches(e.g., capable of switching rapidly relative to frames). Implementationsof the switches operate at radio frequency (RF) such as Ka bandfrequencies. In some embodiments, ferrite switches are used for theswitches, which can provide fast switching, low insertion loss (e.g., donot substantially impact equivalent isotropically radiated power (EIRP)or gain-to-noise-temperature (G/T)), high power handling capabilities,etc.

The illustrated configuration includes multiple levels of terminalgrouping. At a first level, user terminals 110 and/or gateway terminals165 communicate over input and output beams corresponding to feeds. Forexample, each “user feed” 310/320 supports communications for a numberof user terminals 110. At a second level, the input and output beams(and respective feeds) can be grouped into spot beams. For example, eachspot beam can support multiple feeds at different frequencies (e.g.,separate uplink and downlink frequencies) and/or polarizations. At athird level, beams can be grouped into beam groups. For example, asdescribed above, each input subsystem 210 and/or output subsystem 230can have respective receive switches 330 and/or transmit switches 340that can switch between beams in an associated beam group (e.g.,according to input/output (I/O) beam switching patterns 337). At afourth level, beam groups can themselves be grouped by associated beamgroup switching subsystems 250 (e.g., into “sets of beam groups” or“matrix switch groups”). For example, as illustrated in FIG. 2, eachbeam group switching subsystem 250 can selectively couple up to P inputsubsystems 210 with up to P output subsystems 230, so that each beamgroup switching subsystem 250 effectively facilitates communicationswith up to P beam groups (assuming the same P beam groups are associatedwith the input subsystems 210 (for receive traffic) and the outputsubsystems 230 (for transmit traffic)). Further, as illustrated in FIG.3, a single satellite 105 (or group of associated satellites 105) canhave multiple beam group switching subsystems 250, each associated withits own set of beam groups 325 (e.g., its own P beam groups supported byits own P input and/or output subsystems). Accordingly, n beam groupswitching subsystems 250 can support n sets of beam groups 325 a-325 n.Some of these groupings are not explicitly illustrated for the sake ofclarity. For example, while forward-link gateway feed 305 a isillustrated by a single arrow, the forward-link gateway feed 305 a canrepresent (for a given communication) a particular feed of a particularbeam of a particular beam group of a particular set of beam groups 325serviced by one of the particular input subsystems 210 a of a particularbeam group switching subsystem 250 a.

For the sake of clarity, forward pathways (e.g., for forward-linkcommunications) are illustrated by solid arrows, and return pathways(e.g., for return-link communications) are illustrated by dashed arrows.For example, a forward-channel uplink signal is received via aforward-link gateway feed 305 a at a first of the input subsystems 210 aof a first beam group switching subsystem 250 a (e.g., a receive switch330 associated with the input subsystem 210 a is switched to receivefrom the forward-link gateway feed 305 a according to the I/O beamswitching pattern 337 corresponding to the present slot). The trafficfrom the forward-channel uplink signal is routed to a particular one ofthe output subsystems 230 a of the beam group switching subsystem 250 aaccording to the beam group switching pattern 252 corresponding to thepresent slot. The signal (now a forward channel downlink signal) isrouted to one of N forward-link user feeds 320 a corresponding to one ofthe beams of the beam group associated with the particular one of theoutput subsystems 230 a (e.g., a transmit switch 340 associated with theparticular output subsystem 230 a is switched to transmit over theforward-link user feed 320 a according to the I/O beam switching pattern337 corresponding to the present slot).

Similarly, at a next slot, a return-channel uplink signal is receivedvia a return-link user feed 310 a at a first of the input subsystems 210a of a first beam group switching subsystem 250 a (e.g., the receiveswitch 330 associated with the input subsystem 210 a is switched toreceive from the return-link user feed 310 a according to the I/O beamswitching pattern 337 corresponding to the next slot). The traffic fromthe return-channel uplink signal is routed to a particular one of theoutput subsystems 230 a of the beam group switching subsystem 250 aaccording to the beam group switching pattern 252 corresponding to thenext slot. The signal (now a return-channel downlink signal) is routedto one of N return-link gateway feeds 315 a corresponding to one of thebeams of the beam group associated with the particular one of the outputsubsystems 230 a (e.g., a transmit switch 340 associated with theparticular output subsystem 230 a is switched to transmit over thereturn-link gateway feed 315 a according to the I/O beam switchingpattern 337 corresponding to the next slot).

Typically, each of the I/O beam switching pattern 337 and the beam groupswitching pattern 252 defines a certain configuration at each slot ofeach frame, and the slot boundaries of the switching patterns aresynchronized (e.g., lined up). For example, the I/O beam switchingpattern 337 repeats for each of a number of first frames, each having Nslots, and the beam group switching pattern 253 repeats for each of anumber of second frames, each having M slots. The I/O beam switchingpattern 337 can define which input and output beams of its respectivebeam groups to use for communications during each of the N slots of itsframe. The beam group switching pattern 252 can define which inputsubsystems 110 to communicatively couple with each output subsystem 230during each of the M slots of its frame. In some implementations, N andM are equal, so that the I/O beam switching pattern 337 and the beamgroup switching pattern 252 repeat at the same time interval. In otherimplementations, the frame lengths are different, so that the beam groupswitching pattern 252 repeats more or less often than the I/O beamswitching pattern 337. For example, the I/O beam switching pattern 337has 64 slots, and the beam group switching pattern 252 has 128 slots(i.e., the beam group switching pattern 252 repeats half as often as theI/O beam switching pattern 337).

Further, the switching patterns do not necessarily change configurationat each slot of each frame. For example, the I/O beam switching pattern337 can change which input and output beams of its respective outputbeam group to use for receiving and transmitting once per each R slots,and the beam group switching pattern can change which input subsystem210 to communicatively couple with each output subsystem 230 once pereach S slots. In some implementations, R and S are both one, so thateach switching pattern changes its respective configurationsubstantially at each slot boundary. In other implementations, R and Sare different, so that each switching pattern changes its respectiveconfiguration at different rates. Further, R and S are not necessarilyconsistent throughout a frame. For example, the beam group switchingpattern 252 can change its configuration at every slot during someportions of the frame, and can change its configuration less oftenduring other portions of the frame.

In some implementations, sets of frames can be grouped into“super-frames.” For example, as described below, some implementationsinclude a robust beam group switching pattern 252 that repeats at eachframe and does not change over time (e.g., unless certain, relativelyunlikely conditions occur). Other implementations can include a set ofmultiple robust beam group switching patterns 252, where each repeats ateach frame for some amount of time, and the set of robust beam groupswitching patterns 252 repeats over a longer period of time defined by asuper-frame. For example, a number of time windows is defined tocoincide with peak usage times in different time zones. Each time windowis associated with a corresponding robust beam group switching pattern252 that is optimized for load balancing in context of the peak-usagebeams, but the robust beam group switching pattern 252 does not changeduring its corresponding time window (e.g., absent long-term gatewayoutages or other such unlikely conditions).

While certain functionality is described in context of the satellite 105(e.g., satellite configuration 300), some of the functionality involvescoordination between the satellite 105 and one or more gateway terminals165, core nodes 170, and/or other ground systems. For example, sourcingforward-link capacity for a given user beam from multiple gatewayterminals 165 in a shared manner can involve queuing traffic destinedfor user terminals 110 of that user beam and distributing the queuedtraffic across the multiple gateway terminals 165 in a manner thatsupports the shared distribution. Similarly, sinking return-linkcapacity for a given user beam by multiple gateway terminals 165 in ashared manner can involve scheduling traffic from user terminals 110 ofthat user beam to be received via multiple gateway terminals 165 in amanner that supports the shared distribution. This can be effectuated bydistributing and/or scheduling the traffic with respect to gatewayterminals 165 with an awareness of applicable I/O beam switchingpatterns 337 and beam group switching patterns 252. In some embodiments,the gateway terminals 165 are aware of the appropriate switchingpatterns themselves or in conjunction with a gateway controller or othersystem. In other embodiments, the gateway terminals 165 are unaware ofthe appropriate switching patterns, but core nodes in communication withthe gateway terminals 165 are aware of the switching patterns and candeliver traffic to the gateway terminals 165 as appropriate.

The embodiments illustrated in FIGS. 2 and 3 show only certainimplementations of satellite functionality described herein. Differentnumbers and/or types of components can be used in the same or otherconfigurations to provide similar or identical functionality withoutdeparting from the scope of embodiments. For example, as illustrated inFIG. 4, control and storage components can be used to control operationof the switching subsystems in some embodiments. A switch pattern store420 can be used to store I/O beam switching patterns 337 and beam groupswitching patterns 252. These patterns can be provided, as appropriate,to a switch controller 410. The switch controller 410 can be used tocontrol (e.g., direct, synchronize, etc.) switching of receive switches330, transmit switches 340, and/or beam group switching subsystems 250,etc. In other embodiments the switch controller 410 includes one or moreswitch controllers 410 and/or the switch pattern store 420 includes oneor more switch pattern stores 420.

Certain features of robust beam group switching functionality areillustrated using the sample switching patterns shown in FIGS. 5A-6E.Turning first to FIGS. 5A-5D, a non-robust beam group switching patternis illustrated in normal and single-gateway outage conditions, for thesake of context. The beam group switching pattern can be associated witha beam group switching subsystem associated with four beam groups(illustrated as “Grp 1”-“Grp 4”) and four associated gateway terminals165. The “user link schedule” and the “gateway link schedule” aregoverned by an illustrative I/O switching pattern 337 (e.g., effectuatedby receive switches 330 and transmit switches 340). For example, at timeslot 0, the receive and transmit switches for four respective input andoutput subsystems are configured so that beam group 1 is set for useruplink and gateway downlink both on beam 1, beam group 2 is set for useruplink on beam 11 and gateway downlink on beam 10, beam group 3 is setfor user downlink on beam 12 and gateway uplink on beam 12, and beamgroup 4 is set for user downlink on beam 14 and gateway uplink on beam14. These designations are described more fully below.

FIG. 5B shows a functional block diagram corresponding to anillustrative system 500 b in a configuration like the one described fortime slot 0 of FIG. 5A. As illustrated, the system 500 b includes fourreceive switches 330 and four transmit switches 340, coupled with a4-by-4 beam group switching subsystem 250 via respective receivecomponents 510 and transmit components 520 (e.g., appropriateamplifiers, filters, etc.). For example, the receive components 510 andtransmit components 520 include components of the input subsystems 210and output subsystems 230 described above, respectively.

The first beam group serviced by the first receive switch 330 a has ninebeams, including eight user beams and one gateway/user beam (“GW/U”)(e.g., usable by an associated gateway terminal 165 and user terminals110 in the beam's coverage area), and each of the other three groupsserviced by respective receive switches 330 b-330 d has two beams,including one user beam and one gateway/user beam. For example, any ofbeams 1-9 can be used to service user terminals 110 in Grp 1, while thegateway terminal 165 of Grp 1 is serviced using only beam 1. Also, asillustrated, each beam can support an uplink feed and a downlink feed.For example, the “GW/U 1” feed shown as an input to the first receiveswitch 330 a services return-channel uplink traffic for the userterminals 165 of Grp 1 (designated as “U1” in the user link schedule ofFIG. 5A) or forward-channel uplink traffic for the gateway terminal 165of Grp 1 (designated as “U1” in the gateway link schedule of FIG. 5A).Similarly, the “GW/U 1” feed shown as an output to the first transmitswitch 340 a services forward-channel downlink traffic for the userterminals 165 of Grp 1 (designated as “D1” in the user link schedule ofFIG. 5A) or return-channel downlink traffic for the gateway terminal 165of Grp 1 (designated as “D1” in the gateway link schedule of FIG. 5A).It is noted that the “U” designation in FIG. 5A refers to “uplink”(e.g., for user terminals in return-channel communication or for gatewayterminals in forward-channel communication) while the “U” designation inFIG. 5B refers to “user” (e.g., a beam designated for use by userterminals, not by gateway terminals).

The “matrix switch schedule” of FIG. 5A is governed by an illustrativebeam group switching pattern 252 (e.g., effectuated by the beam groupswitching subsystem 250 of FIG. 5B). The white cells with black textindicate return-link configurations, and the black cells with white textindicate forward-link configurations. In the non-robust pattern examplesshown in FIGS. 5A-5D, the matrix switch schedule is configured simplyfor pass-through. In every time slot, the input subsystem 210 associatedwith beam group N is coupled with the output subsystem 230 associatedwith beam group N. As illustrated in FIG. 5B, receive switches 330 a-330d are coupled via the beam group switching subsystem 250 with transmitswitches 340 a-340 d, respectively.

For example, the gateway terminal 165 associated with beam 1 of beamgroup 1 (“GW/U 1” in FIG. 5B) services the capacity for all the userterminals 110 in beam group 1 for all time slots. As shown in FIG. 5Afor time slot 0, the first receive switch 330 a and the first transmitswitch 340 a are coupled through the beam group switching subsystem 250to form a return-channel pathway. As illustrated in FIG. 5B, the pathwayeffectively passes traffic received on the “GW/U 1” return-channel useruplink feed (“U1” on the User Schedule of FIG. 5A) to the “GW/U 1”return-channel gateway downlink feed (“D1” on the Gateway Schedule ofFIG. 5A).

In the normal condition, all four gateway terminals 165 are operational,and the gateways can support full capacity. In this pass-throughconfiguration, however, any user terminals 110 being serviced by aparticular gateway terminal 165 can lose all capacity for the durationof the gateway outage (or until a new switch configuration can beestablished. For example, FIG. 5C illustrates a condition during whichthe gateway terminal 165 associated with beam group 1 isnon-operational. As shown by the shaded cells, no communications aresupported on any beams in beam group 1 for the entire duration of theoutage. This condition is also illustrated in FIG. 5D for time slot 0.The “GW/U 1” return-channel gateway downlink feed is shown as black withwhite text to indicate that the gateway terminal 165 associated withthat downlink feed is non-operational. With a non-operational gatewayterminal 165 in the path, traffic cannot be communicated via that feed.Similarly, in any time slots having the first receive switch 330 a setto select its “GW/U 1” feed, the first beam group would be attempting toreceive forward-channel uplink traffic from the non-operational gatewayterminal.

FIGS. 6A-6E show illustrative robust switching patterns and anillustrative system embodiment governed by those switching patterns, allcorresponding to the non-robust cases described in FIGS. 5A-5D,respectively. Turning to FIG. 6A, an illustrative robust beam groupswitching pattern is shown in a normal condition. The robust beam groupswitching pattern is associated with a beam group switching subsystem250 associated with four beam groups (illustrated as “Grp 1”-“Grp 4”)and four associated gateway terminals 165. To facilitate comparison, the“user link schedule” and the “gateway link schedule” are governed by thesame illustrative I/O switching pattern 337 described with respect toFIGS. 5A-5D. Further, as in FIGS. 5A-5D, the first beam group has ninebeams, including eight user beams and one gateway/user beam (e.g.,usable by an associated gateway terminal 165 and user terminals 110 inthe beam's coverage area), and each of the other three groups has twobeams, including one user beam and one gateway/user beam. Unlike thenon-robust (e.g., pass-through) matrix switch configuration in FIGS.5A-5D, FIG. 6A shows a more robust matrix switch schedule that changeswhich input beam group is coupled with which output beam group in eachtime slot.

The “matrix switch schedule” is governed by an illustrative robust beamgroup switching pattern 252 (e.g., effectuated by a beam group switchingsubsystem 250). The white cells with black text indicate return-linkconfigurations, and the black cells with white text indicateforward-link configurations. For the sake of illustration, in time slot0, the input portion of beam group 1 (i.e., the “U” designation in “Grp1”) is designated as “U1” in the User Link Schedule, indicating that thereceive switch 330 of the input subsystem 210 for beam group 1 isswitched to receive a return-channel user uplink feed on beam 1. Thematrix switch schedule indicates that, in time slot 0, Input 1(corresponding to the input subsystem 210 of the first beam group) iscoupled with Output 2 (corresponding to the output subsystem 210 of thesecond beam group). The output portion of beam group 2 (i.e., the “D”designation in “Grp 2”) is designated as “D10” in the Gateway LinkSchedule, indicating that the transmit switch 330 of the outputsubsystem 230 for beam group 2 is switched to transmit a return-channelgateway downlink feed on beam 10.

FIG. 6B shows a functional block diagram corresponding to anillustrative system 600 b in a configuration like the one described fortime slot 0 of FIG. 6A. For the sake of comparison, the system 600 b ofFIG. 6B is essentially identical to the system 500 b of FIG. 500b ,except that the beam group switching subsystem 250 is not configured asa pass-through. As illustrated, according to time slot 0 of the matrixswitch schedule, the first receive switch 330 a is coupled with thesecond transmit switch 340 b (via respective receive components 510 aand transmit components 520 b and the beam group switching subsystem250); the second receive switch 330 b is coupled with the first transmitswitch 340 a; the third receive switch 330 c is coupled with the fourthtransmit switch 340 d; and the fourth receive switch 330 d is coupledwith the third transmit switch 340 c. For example, a return-channelpathway is effectively formed between the gateway terminal of Grp 1 anduser terminals on beam 11. The “U 11” return-channel user uplink feed(“U11” on the User Schedule of FIG. 6A) passes return-channel traffic intime slot 0 to the “GW/U 1” return-channel gateway downlink feed (“D1”on the Gateway Schedule of FIG. 6A), via the second receive switch 330b, the second receive components 510 b, the beam group switchingsubsystem 250, the first transmit components 520 a, and the firsttransmit switch 340 a. Effectively, during the illustrated time slot,the gateway terminal of Grp 1 (on beam 1) is servicing return-channeltraffic for user terminals in Grp 2 (on beam 11), the gateway terminalof Grp 2 (on beam 10) is servicing return-channel traffic for userterminals in Grp 1 (on beam 1), the gateway terminal of Grp 3 (on beam12) is servicing forward-channel traffic for user terminals in Grp 4 (onbeam 14), and the gateway terminal of Grp 4 (on beam 14) is servicingforward-channel traffic for user terminals in Grp 3 (on beam 12).

Comparing time slot 0 with time slot 8 in FIG. 6A, the user link andgateway link schedules for Grp 1 are the same, but the matrix switchschedules are different. Again, the input portion of beam group 1 isdesignated as “U1” in the User Link Schedule, indicating areturn-channel user uplink feed on beam 1. However, the matrix switchschedule indicates that, in time slot 8, Input 1 is coupled withOutput 1. The link schedules indicate that the output portion of beamgroup 1 is designated as “D1” in the Gateway Link Schedule, indicating areturn-channel gateway downlink feed on beam 1. Accordingly, over thecourse of the sixteen illustrative time slots, beam 1 is used twice forreturn-channel user uplink traffic; but the downlink handling of thereturn-channel traffic on beam 1 is shared between first and secondgateway terminals 165.

One forward-link example is illustrated by the downlink traffic on beam13. The link schedules indicate that the output portion of beam group 3shows “D13” (indicating that the transmit switch 330 of the outputsubsystem 230 for beam group 3 is switched to transmit a forward-channeluser downlink feed on beam 13) for time slots 1, 2, 3, and 9. Accordingto the matrix switch schedule for those time slots, the input subsystem230 of beam group 3 is coupled with the output subsystems 210 of beamgroups 3, 4, 3, and 1, respectively. As such, over the course of thesixteen illustrative time slots, beam 13 is being used forforward-channel downlink traffic during four time slots (i.e., 25% ofthe time), and its forward-link capacity is being sourced over thosefour time slots by three different gateway terminals 165 (i.e., half bythe gateway terminal 165 of beam group 3, and a quarter each by thegateway terminals 165 of beam groups 1 and 4).

In the illustrated normal condition, all four gateway terminals 165 areoperational, and the gateways can support full capacity. Because theuser links are being serviced in a shared manner by multiple gatewayterminals 165, gateway outages can occur without completely eliminatingcapacity to all the user feeds in a particular group. For example, FIG.6C illustrates a condition during which the gateway terminal 165associated with beam group 1 is non-operational. The shaded cellsindicate effects of an outage condition regarding the gateway terminal165 of beam group 1 (“Gateway 1”). For example, the entire columncorresponding to the link schedule for Gateway 1 is shaded to indicatethat Gateway 1 cannot support any traffic during its outage. The valuesin the shaded cells are still present to indicate that the embodiment ofthe switches will continue to try to switch Gateway 1 into theconfiguration according to the switch patterns, even though it isnon-functional.

The examples described in context of FIG. 6A can be shown with referenceto FIG. 6C to illustrate features of robust switching patterns. In thereturn-link example, beam 1 is being used for return-channel user uplinktraffic during 2 of the 16 time slots (⅛ of the time), and is servicedhalf by Gateway 1 and half by Gateway 2 (i.e., each for one of the twotime slots). With the outage of Gateway 1, the return link capacity onbeam one cannot be serviced during time slot 8 of each frame, but it canstill be serviced during time slot 0 of each frame. Accordingly, thereturn-link capacity for beam 1 is degraded by approximately one half.

The outage cases of time slots 0 and 8 are shown in FIGS. 6D and 6E,respectively. Comparing the no-outage case of FIG. 6B to the outage caseof FIG. 6D, the outage of Gateway 1 impacts its ability in time slot 0to sink return-channel traffic from user terminals in beam 11 (Grp 2users). However, the outage has no impact during time slot 0 onreturn-channel traffic for users in beam 1 (Grp 1 users), as those usersare being serviced by Gateway 2 via beam 10 during that time slot. Intime slot 8, different gateway terminals are servicing different beams.For example, return-channel traffic for the users in beam 1 cannot besupported during time slot 8 due to the outage of Gateway 1. ComparingFIGS. 6D and 6E, the robust switching pattern allows users in beam 1 tokeep some return-channel capacity even in the face of a Gateway 1outage.

Returning to FIG. 6C, in an illustrative forward-link example, beam 13is being used for forward-channel user downlink traffic during 4 of the16 time slots (¼ of the time), and is serviced one quarter of the timeby Gateway 1, half the time by Gateway 3, and the remaining quarter ofthe time by Gateway 4 (i.e., 1, 2, and 1 slots each, respectively). Withthe outage of Gateway 1, the return link capacity on beam one cannot beserviced during time slot 9 of each frame, but it can still be servicedduring time slots 1, 2, and 3 of each frame. Accordingly, theforward-link capacity for beam 13 is degraded by approximatelyone-quarter. Similarly, an outage of Gateway 2 would have no effect onforward-link capacity for beam 13, an outage of Gateway 3 would degradethe forward-link capacity for beam 13 by approximately one-half, and anoutage of Gateway 4 would degrade the forward-link capacity for beam 13by approximately one-quarter. Indeed, Gateways 1, 3, and 4 would allhave to be non-operational at the same time to bring the forward-linkcapacity for beam 13 down to zero.

FIGS. 7A-7D show four configurations of an illustrative system 700 forsourcing forward-link capacity to a user beam in a shared manner amongfour gateway terminals. As illustrated, the system 700 includes fourreceive switches 330 and four transmit switches 340, coupled with a4-by-4 beam group switching subsystem 250 via respective receivecomponents 510 and transmit components 520. Each of FIGS. 7A-7D showsthe system 700 in one of four possible configurations for sourcingforward-channel capacity to user terminals in beam 3 from each of fourgateways (via respective beams). For example, FIG. 7A shows Gateway 1(on beam 1) sourcing forward-channel capacity for users in beam 3, andFIG. 7B shows Gateway 2 (on beam 10) sourcing forward-channel capacityfor users in beam 3. Only the relevant communication pathway through thesystem to users in beam 3 is shown for clarity, though users in otherbeam groups would typically be coupled gateways in other beam groups viathe beam group switching subsystem 250 (e.g., as described above).

FIGS. 8A-8D show four configurations of an illustrative system 800 forsinking return-link capacity from a user beam in a shared manner amongfour gateway terminals. The system 800 of FIGS. 8A-8D is identical tothe system 700 of FIGS. 7A-7D, except that it is configured forservicing return-channel traffic from user terminals in beam 3 from eachof four gateways (via respective beams). For example, FIG. 8A showsGateway 1 (on beam 1) sinking return-channel capacity for users in beam3, and FIG. 8B shows Gateway 2 (on beam 10) sinking return-channelcapacity for users in beam 3. Again, only the relevant communicationpathway through the system from users in beam 3 is shown for clarity,though users in other beam groups would typically be coupled gateways inother beam groups via the beam group switching subsystem 250 (e.g., asdescribed above).

FIG. 9 shows a flow diagram of an illustrative method 900 for robustsharing of gateway resources between gateway terminals and userterminals over fixed location beams, according to various embodiments.As described above, embodiments operate in context of a hub-spokesatellite architecture in which at least one satellite is incommunication with multiple gateway and user terminals via input andoutput beams. Embodiments of the method 900 begin at stage 904 bysequentially switching a set of input subsystems of a satellite to eachreceive traffic via a respective input beam during each of a number oftime slots according to an input switching pattern. For example, thesatellite includes input subsystems that have respective receiveswitches that can switch among a number of associated input beams. Somebeams can be input gateway beams for forward-link traffic (i.e.,forward-channel uplink beams), and other beams can be input user beamsfor return-link traffic (i.e., return-channel uplink beams). The inputswitching pattern defines, at each time slot, which of the input beamsis being used by each of the input subsystems for receiving traffic.Various implementations of the input switching pattern can change theconfiguration of the switches as frequently or as infrequently asdesirable. For example, switching the input subsystems can involveswitching at each time slot, switching periodically at equal intervalsof time slots, or switching according to any other suitable pattern.

Embodiments of the method 900 continue at stage 908, by sequentiallyswitching a set of output subsystems of the satellite to each transmitthe traffic via a respective output beam during each of the time slotsaccording to an output switching pattern. For example, the satelliteincludes output subsystems that have respective transmit switches thatcan switch among a number of associated output beams. Some output beamscan be output gateway beams for return-link traffic (i.e.,return-channel downlink beams), and other output beams can be outputuser beams for forward-link traffic (i.e., forward-channel downlinkbeams). The output switching pattern defines, at each time slot, whichof the output beams is being used by each of the output subsystems fortransmitting traffic. Various implementations of the output switchingpattern can change the configuration as frequently or as infrequently asdesirable. For example, the receive and transmit switches can changeconfiguration at the same or different times, according to the same ordifferent patterns, etc. (e.g., though typically synchronously withrespect to the slot boundaries).

At stage 912, a beam group switching subsystem is sequentially switchedat each of the time slots according to a beam group switching pattern,thereby coupling each input subsystem with one of the output subsystemsduring each time slot. For example, the satellite includes one or morebeam group switching subsystems (e.g., matrix switches), each incommunication with a respective set of input subsystems and set ofoutput subsystems. Each input subsystem and each output subsystem isassociated with one of a number of beam groups (e.g., each beam grouphaving a number of beams, and each beam supporting one or more userand/or gateway beams), so that each beam group switching subsystem isassociated with a set of beam groups corresponding to the beam groups ofits respective set of input subsystems and set of output subsystems.Various implementations of the beam group switching pattern can changethe configuration of the beam group switching subsystem as frequently oras infrequently as desirable. For example, all receive, transmit, andbeam group switches can change configuration at the same time (e.g.,substantially at each slot boundary). Alternatively, any of the receive,transmit, and beam group switches can differ in how often theirrespective configurations change to allow for many different switchingconfiguration options. As used herein, “switching” the input subsystems,output subsystems, and/or beam switching subsystems can generally referto changing or maintaining a particular configuration, and is notintended to be limited to altering one or more switches. For example,the beam group switching subsystem can be said to “switch” at each timeslot, even if the configuration of connections between input and outputsubsystems does not change at each time slot.

Switching the beam group switching subsystem according to the beam groupswitching pattern distributes capacity to each user beam among multiplegateway beams in a shared manner. In various embodiments, the beam groupswitching pattern is configured (e.g., designed, optimized, etc.) towardone or more particular goals. Configuring the pattern toward a goal doesnot necessitate meeting that goal; rather, the goal can drive whichdecisions are made when facing trade-offs. In some embodiments, the beamgroup switching pattern is configured so that distributing the secondaggregate capacity according to the beam group switching pattern whenonly Q of the P respective gateway terminals are operational minimizesworst-case degradation in aggregate over the output user beams (e.g., asin the “min-max” scenario described above).

In other embodiments, the beam group switching pattern is configured sothat distributing the second aggregate capacity according to the beamgroup switching pattern when only Q of the P respective gatewayterminals are operational prioritizes capacity distribution to apredetermined subset of output user beams. One technique forprioritizing capacity distribution is to configure the beam groupswitching pattern to distribute a relatively larger proportion ofcapacity to each of a number of designated high-priority output userbeams among each of one or more high-priority input gateway beams in ashared manner. For example, one or more particular beam group switchingsubsystems can be designated for high-priority beams and can be incommunication with the higher-reliability gateway beams andhigher-priority user beams to facilitate coupling there-between.Alternatively, the switching pattern can be configured to allot moreslots for higher-priority user beams to the higher-reliability gatewaybeams. Another technique for prioritizing capacity distribution is toincrease gateway diversity for higher-priority user beams. The beamgroup switching subsystem can be switched according to the beam groupswitching pattern in such a way that distributes capacity to eachhigh-priority output user beam among a relatively larger number of inputgateway beams in a shared manner than to the output user beams notdesignated as high-priority output user beams. For example, a particularbeam group switching subsystem facilitates sharing of capacity to itsuser beams among up to eight gateway beams. On average, higher-priorityuser beams have capacity servicing shared by more of the eight possiblegateway beams (e.g., seven or eight), while lower-priority user beamshave capacity servicing shared by fewer of the eight gateways (e.g., oneor two). In this way, when any one gateway becomes non-operational,there is a lower magnitude of impact from the non-operational gateway onthe aggregate capacity for the higher-priority user beams.

Other constraints can be placed on the beam group switching pattern(e.g., and on the input and/or output switching patterns). One suchconstraint is that satellite power requirements can limit which types oftraffic can be supported in which ways. For example, implementations canbe configured to balance forward-link draw and return-link drawaccording to satellite specifications. Another such constraint is that,in the hub-spoke architecture, traffic can be limited to flow from agateway link to a user link or from a user link to a gateway link, butnot from users to users or from gateways to gateways. For example, whenan input subsystem is switched to receive from an input gateway beam,the beam group switching subsystem should couple that input system to anoutput subsystem switched to transmit on an output user beam.Accordingly, the beam group switching pattern can be configured so as toensure hub-spoke types of communications (e.g., or to avoid disturbingthose types of communications being facilitated by input and/or outputswitching patterns).

FIG. 10 shows a flow diagram of an illustrative method 1000 fordistributing capacity to each output user beam from multiple of thegateway input beams in a shared manner. The method 1000 begins at stage1004 by distributing a first aggregate capacity to the output user beamsin a shared manner among P of the input gateway beams according to thebeam group switching pattern when P respective gateway terminalsassociated with the P input gateway beams are operational. For example,the beam group switching subsystem is capable of coupling any of eightinput gateway beams (associated with eight gateway terminals) to any ofeight user output beams at any time slot for forward-link capacitydistribution; and the beam group switching subsystem is capable ofcoupling any of eight output gateway beams (associated with eightgateway terminals) to any of eight user input beams at any time slot forreturn-link capacity distribution. For the sake of illustration,capacity for any particular user beam can be serviced in a shared mannerby any or all eight of the gateway beams over the course of a frame oftime slots.

At stage 1008, one or more gateway terminals becomes non-operational(e.g., temporarily), but capacity continues to be distributed accordingto the same beam group switching pattern. In particular, a secondaggregate capacity is distributed to the output user beams in a sharedmanner among Q of the P input gateway beams according to the beam groupswitching pattern when only Q of the P respective gateway terminals areoperational. For example, one gateway terminal experiences rain fade toan extent that it becomes temporarily non-operational, but the beamgroup switching subsystem continues to switch according to the robustbeam group switching pattern. Ground segment components (e.g., corenodes, etc.) can redistribute traffic among the still-operationalgateway terminals, but overall capacity is effectively reduced to asecond capacity level. Still, the beam group switching pattern isdesigned to be robust enough so that the output user beams continue tohave at least a minimum threshold amount of capacity (in aggregate).

In some embodiments, at stage 1012, the satellite receives an indicationthat a long-term outage in any of the P respective gateway terminals hasbeen detected. For example, the ground segment detects a gatewaymalfunction (e.g., based on loopback traffic, or other techniques), andcommunicates an indication to the satellite, accordingly. In response toreceiving the indication, at stage 1016, some embodiments distribute athird aggregate capacity to each associated output subsystem in a sharedmanner from fewer than the P input gateway beams (i.e., some or all ofthe remaining operable gateway terminals) according to a second(alternative) beam group switching pattern. In some implementations, thesecond beam group switching pattern is received via an input gatewaybeam (e.g., from one of the operable gateway terminals). In otherimplementations, the satellite has a set of one or more alternativesecond beam group switching patterns, and it can select an appropriatealternate pattern according to the indication (e.g., according to whichgateway terminal is determined to manifest the long-term outage). Forexample, the alternative beam group switching pattern is optimized forthe particular gateway outage, so that the third aggregate capacity canbe greater than the second aggregate capacity. While the method 1000focuses on forward-link capacity sharing, similar techniques can beapplied to return-link capacity sharing, for example, as describedherein.

FIGS. 11A and 11B show flow diagrams of another illustrative method 1100for robust sharing of gateway resources between gateway terminals anduser terminals over fixed location beams in forward-link and return-linkconfigurations, respectively, according to various embodiments.Beginning with FIG. 11A, embodiments begin at stage 1104 by configuringa first input subsystem of a satellite in a first time slot to receivevia a first gateway input beam, and a second input subsystem of thesatellite in a second time slot to receive via a second gateway inputbeam. In some implementations, configuring the input subsystems involvesswitching respective receive switches according to an input switchingpattern that defines which input beam to use for receiving by each inputsubsystem in each of a number of time slots. For example, each inputsubsystem is associated with a beam group having respective gatewaybeams, including respective input gateway and output gateway beams forhandling forward-link and return-link traffic, respectively. The beamgroup of each input subsystem can also have user beams, includingrespective input user and output user beams for handling return-link andforward-link traffic, respectively.

Stages 1108 and 1112 receive a forward-link communication destined for atarget user terminal from two gateway beams at two time slots. At stage1108, in a first time slot, a first portion of a forward-linkcommunication is received by the first input subsystem from a firstgateway terminal via the first input gateway beam. At stage 1112, in asecond time slot, a second portion of the forward-link communication isreceived by the second input subsystem from a second first gatewayterminal via the second input gateway beam.

Stages 1116 and 1120 configure a beam group switching subsystem todirect each of the two portions of the forward-link communication to anappropriate output subsystem in the two time slots. At stage 1116, inthe first time slot, the beam group switching subsystem couples thefirst input subsystem with a particular output subsystem according to abeam group switching pattern. At stage 1120, in the second time slot,the beam group switching subsystem couples the second input subsystemwith the particular output subsystem according to the beam groupswitching pattern. The particular output subsystem is associated withone of a number of beam groups that supports a number of output beamsincluding an output user beam that services the target user terminal.The beam group switching pattern defines which input subsystem iscoupled with which output subsystem in each time slot.

Stages 1124 and 1128 configure the output subsystem to transmit via thedesired user beam during both of the time slots and transmit thetraffic, accordingly. At stage 1124, the output subsystem is configuredin the first time slot to transmit via the output user beam, and theoutput subsystem is configured in the second time slot to transmit viathe output user beam. In some implementations, the output systems areconfigured by switching according to an output switching pattern thatdefines which of the output beams to use for transmitting by the outputsubsystem in each of the time slots. In one illustrative scenario, thefirst and second time slots are adjacent in time, and configuring theoutput system in the second time slot involves keeping the transmitswitch of the output subsystem in the same configuration (e.g., to keeptransmitting on the same output beam). In another illustrative scenario,the first and second time slots are non-adjacent in time, andconfiguring the output system in the second time slot involves switchingthe transmit switch in time slot two back to the configuration from timeslot one (e.g., to return to transmitting on the output beam for thetarget user terminal). At stage 1128, the first and second portions ofthe forward-link communication are transmitted to the target userterminal in the first and second time slots, respectively, via theoutput user beam.

Continuing with FIG. 11B, the method 1100 b proceeds to handlereturn-link traffic. At stage 1140, the first input subsystem isconfigured in a third time slot to receive a first portion of areturn-link communication originating from a source user terminal via auser input beam. At stage 1144, the first input subsystem is configuredin a fourth time slot to receive a second portion of the return-linkcommunication originating from the source user terminal via the userinput beam. In some implementations, the first input subsystem isswitched at some or all time slots according to an input switchingpattern. As described above, the third and fourth time slots may or maynot be adjacent in time. Further, the third and fourth time slots may bebefore, after, or interspersed with the first and second time slots. Forexample, the order of time slots can be first, third, second, fourth;first, fifth, second, sixth, seventh, third, eighth, ninth, fourth; etc.

At stage 1148, the first input subsystem is coupled with the firstoutput subsystem by the beam group switching subsystem according to thebeam group switching pattern in the third time slot. At stage 1152, thefirst input subsystem is coupled with the second output subsystem by thebeam group switching subsystem according to the beam group switchingpattern in the fourth time slot. At stages 1156 and 1160, respectively,a first of the output subsystems is configured in the third time slot totransmit via a first gateway output beam, and a second of the outputsubsystems is configured in the fourth time slot to transmit via asecond gateway output beam. For example, the output subsystems areconfigured by switching according to an output switching pattern. Atstage 1164, the first and second portions of the return-linkcommunication are transmitted to the first and second gateway terminalsin the first and second time slots, respectively, via the first andsecond output gateway beams.

The methods disclosed herein include one or more actions for achievingthe described method. The method and/or actions can be interchanged withone another without departing from the scope of the claims. In otherwords, unless a specific order of actions is specified, the order and/oruse of specific actions can be modified without departing from the scopeof the claims.

The various operations of methods and functions of certain systemcomponents described above can be performed by any suitable meanscapable of performing the corresponding functions. These means can beimplemented, in whole or in part, in hardware. Thus, they can includeone or more Application Specific Integrated Circuits (ASICs) adapted toperform a subset of the applicable functions in hardware. Alternatively,the functions can be performed by one or more other processing units (orcores), on one or more integrated circuits (ICs). In other embodiments,other types of integrated circuits can be used (e.g.,Structured/Platform ASICs, Field Programmable Gate Arrays (FPGAs), andother Semi-Custom ICs), which can be programmed. Each can also beimplemented, in whole or in part, with instructions embodied in acomputer-readable medium, formatted to be executed by one or moregeneral or application specific controllers. Embodiments can also beconfigured to support plug-and-play functionality (e.g., through theDigital Living Network Alliance (DLNA) standard), wireless networking(e.g., through the 802.11 standard), etc.

The steps of a method or algorithm or other functionality described inconnection with the present disclosure, can be embodied directly inhardware, in a software module executed by a processor, or in acombination of the two. A software module can reside in any form oftangible storage medium. Some examples of storage media that can be usedinclude random access memory (RAM), read only memory (ROM), flashmemory, EPROM memory, EEPROM memory, registers, a hard disk, a removabledisk, a CD-ROM and so forth. A storage medium can be coupled to aprocessor such that the processor can read information from, and writeinformation to, the storage medium. In the alternative, the storagemedium can be integral to the processor.

A software module can be a single instruction, or many instructions, andcan be distributed over several different code segments, among differentprograms, and across multiple storage media. Thus, a computer programproduct can perform operations presented herein. For example, such acomputer program product can be a computer readable tangible mediumhaving instructions tangibly stored (and/or encoded) thereon, theinstructions being executable by one or more processors to perform theoperations described herein. The computer program product can includepackaging material. Software or instructions can also be transmittedover a transmission medium. For example, software can be transmittedfrom a website, server, or other remote source using a transmissionmedium such as a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technology such as infrared, radio,or microwave.

Other examples and implementations are within the scope and spirit ofthe disclosure and appended claims. For example, features implementingfunctions can also be physically located at various positions, includingbeing distributed such that portions of functions are implemented atdifferent physical locations. Also, as used herein, including in theclaims, “or” as used in a list of items prefaced by “at least one of”indicates a disjunctive list such that, for example, a list of “at leastone of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., Aand B and C). Further, the term “exemplary” does not mean that thedescribed example is preferred or better than other examples.

Various changes, substitutions, and alterations to the techniquesdescribed herein can be made without departing from the technology ofthe teachings as defined by the appended claims. Moreover, the scope ofthe disclosure and claims is not limited to the particular aspects ofthe process, machine, manufacture, composition of matter, means,methods, and actions described above. Processes, machines, manufacture,compositions of matter, means, methods, or actions, presently existingor later to be developed, that perform substantially the same functionor achieve substantially the same result as the corresponding aspectsdescribed herein can be utilized. Accordingly, the appended claimsinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or actions.

1. (canceled)
 2. A satellite comprising: input subsystems configured toreceive communications via a plurality of input beams; output subsystemsconfigured to transmit the communications via a plurality of outputbeams; and a beam group switching subsystem configured to selectivelycouple any one of the input subsystems with any respective one of theoutput subsystems, such that: for first time slots of a first frame, thebeam group switching subsystem is to couple each one of the outputsubsystems with a corresponding one of the input subsystems according toa non-robust beam group switching pattern; and for second time slots ofa second frame, the beam group switching subsystem is to sequentiallycouple at least one of the output subsystems sequentially with two ormore of the input subsystems according to a robust beam group switchingpattern.
 3. The satellite of claim 2, wherein: the plurality of inputbeams and the plurality of output beams are segregated into a pluralityof beam groups, such that each beam group of the plurality of beamgroups comprises a respective subset of the plurality of input beams anda respective subset of the plurality of output beams; and each beamgroup is associated with a respective one of the input subsystems and arespective one of the output subsystems, such that, for each beam group,the respective one of the input subsystems is to receive communicationsonly via the respective subset of the plurality of input beams of thebeam group, and the respective one of the output subsystems is totransmit communications only via the respective subset of the pluralityof output beams of the beam group.
 4. The satellite of claim 3, wherein:the plurality of input beams and the plurality of output beamscorrespond to user beams and gateway beams, such that each user beamcomprises a respective one of the input beams and a respective one ofthe output beams that enable communications with a respective set ofuser terminals, and each gateway beam comprises a respective one of theinput beams and a respective one of the output beams that enablecommunications with at least a respective gateway terminal; and eachbeam group comprises a gateway beam and a plurality of user beams. 5.The satellite of claim 3, wherein: for each of the first time slots andthe second time slots, according to a first input/output (I/O) switchingpattern and according to a second input/output (I/O) switching pattern,respectively, each of the input subsystems selects a respective one ofthe plurality of input beams, and each of the output subsystems selectsa respective one of the plurality of output beams, such that: for thefirst time slots, selectively coupling the input subsystems with theoutput subsystems by the beam group switching subsystem couples selectedones of the plurality of input beams with selected ones of the pluralityof output beams according to the first I/O switching pattern and thenon-robust beam group switching pattern; and for the second time slots,selectively coupling the input subsystems with the output subsystems bythe beam group switching subsystem couples selected ones of theplurality of input beams with selected ones of the plurality of outputbeams according to the second I/O switching pattern and the robust beamgroup switching pattern.
 6. The satellite of claim 2, wherein: the beamgroup switching subsystem comprises an N-by-N switch to couple any of Ninputs with any of N outputs; each of the N inputs is coupled with arespective one of N of the input subsystems; each of the N outputs iscoupled with a respective one of N of the output subsystems; and theN-by-N switch is to operate as a pass-through during the first frame,such that each one of the N inputs remains coupled with a correspondingone of the N outputs for the first time slots.
 7. The satellite of claim6, wherein: during the second frame, the N-by-N switch is to operate,such that at least one of the N outputs is sequentially coupled with twoor more of the N inputs.
 8. The satellite of claim 6, wherein the switchis a matrix switch that provides full non-blocking cross-connectivitybetween all of the N inputs and all of the N outputs.
 9. The satelliteof claim 3, wherein: the beam group switching subsystem comprises aplurality of inputs; each of the input subsystems comprises a respectivereceive switch; and each respective receive switch has a receive switchoutput and a plurality of receive switch inputs, the receive switchoutput coupled with a respective one of the inputs of the beam groupswitching subsystem, and each of the plurality of receive switch inputscoupled to a respective one of the subset of the plurality of inputbeams of the associated beam group.
 10. The satellite of claim 9,further comprising: a plurality of receive components, wherein thereceive switch output of each respective receive switch is coupled withthe respective one of the inputs of the beam group switching subsystemvia a respective one of the receive components.
 11. The satellite ofclaim 9, further comprising: an antenna having a plurality of inputfeeds associated with the plurality of input beams; and each of theplurality of receive switch inputs is coupled with a respective one ofthe plurality of input feeds by which to receive the communications. 12.The satellite of claim 11, wherein each of the plurality of input feedsis associated with a respective one of the plurality of input beams. 13.The satellite of claim 3, wherein: the beam group switching subsystemcomprises a plurality of outputs; each of the output subsystemscomprises a respective transmit switch; and each respective transmitswitch has a transmit switch input and a plurality of transmit switchoutputs, the transmit switch input coupled with a respective one of theoutputs of the beam group switching subsystem, and each of the pluralityof transmit switch outputs coupled to a respective one of the subset ofthe plurality of output beams of the associated beam group.
 14. Thesatellite of claim 13, further comprising: a plurality of transmitcomponents, wherein the transmit switch input of each respectivetransmit switch is coupled with the respective one of the outputs of thebeam group switching subsystem via a respective one of the transmitcomponents.
 15. The satellite of claim 13, further comprising: anantenna having a plurality of output feeds associated with the pluralityof output beams; and each of the plurality of transmit switch inputs iscoupled with a respective one of the plurality of output feeds by whichto transmit the communications via the respective one of the subset ofthe plurality of output beams of the respective beam group.
 16. Thesatellite of claim 15, wherein each of the plurality of output feeds isassociated with a respective one of the plurality of output beams. 17.The satellite of claim 2, wherein: the input subsystems are configuredto receive forward-link communications from a plurality of gatewayterminals via the plurality of input beams; during the first time slots,all of the plurality of gateways are operational; and during the secondtime slots, at least one of the plurality of gateways isnon-operational.
 18. The satellite of claim 2, wherein: during the firsttime slots and the second time slots, all of the plurality of gatewaysare operational.
 19. The satellite of claim 2, wherein: for second timeslots of a second frame, the beam group switching subsystem is tosequentially couple each of the output subsystems sequentially with twoor more of the input subsystems according to the robust beam groupswitching pattern.
 20. The satellite of claim 2, wherein: each inputsubsystem is associated with a respective one of a plurality of beamgroups, each beam group comprising a gateway beam associated with arespective one of a plurality of gateways, such that: for the first timeslots, a signal path to each of the output subsystems is provided from asingle respective one of the plurality of gateways; and for the secondtime slots, the signal path to each of the output subsystems is sharedamong at least two of the plurality of gateways.
 21. The satellite ofclaim 2, wherein: at least a portion of the communications are receivedfrom and transmitted to a plurality of gateway terminals; and the beamgroup switching subsystem is configured to begin operating according tothe robust beam group switching pattern in response to a detection thatthe at least one of the plurality of gateways is non-operational. 22.The satellite of claim 2, wherein: the satellite comprises N inputsubsystems and N output subsystems; the beam group switching subsystemis one of a plurality of beam group switching subsystems, each beamgroup switching subsystem comprising a respective P-by-P switch tocouple any of a respective P inputs with any of a respective P outputs;each beam group switching subsystem is associated with a corresponding Pinput subsystems of the N input subsystems and a corresponding P outputsubsystems of the N output subsystems, where P is less than N; and foreach beam group switching subsystem, each of the respective P inputs iscoupled with a respective one of the corresponding P input subsystems,and each of the respective P outputs is coupled with a respective one ofthe corresponding P output subsystems.
 23. The satellite of claim 2,wherein: the plurality of input beams and the plurality of output beamscorrespond to user beams and gateway beams, such that each user beamcomprises a respective one of the input beams and a respective one ofthe output beams that enable communications with a respective set ofuser terminals, and each gateway beam comprises a respective one of theinput beams and a respective one of the output beams that enablecommunications with at least a respective gateway terminal; the inputsubsystems are to receive forward-link communications via at least someof the gateway beams and to receive return-link communications via atleast some of the user beams; and the output subsystems are to transmitthe forward-link communications via the at least some of the user beamsand to transmit the return-link communications via the at least some ofthe gateway beams.
 24. The satellite of claim 2, wherein the robust beamgroup switching pattern is received at the satellite via a groundsegment component.
 25. The satellite of claim 2, wherein the robust beamgroup switching pattern is one of a set of alternate beam groupswitching patterns stored at the satellite.
 26. The satellite of claim2, wherein: the robust beam group switching pattern is one of a set ofalternate beam group switching patterns; a first of the set of alternatebeam group switching patterns corresponds to a first of the plurality ofgateways being non-operational; and a second of the set of alternatebeam group switching patterns corresponds to a second of the pluralityof gateways being non-operational.
 27. The satellite of claim 26,wherein: the second of the set of alternate beam group switchingpatterns corresponds further to the first of the plurality of gatewaysbeing non-operational.
 28. The satellite of claim 2, wherein: theplurality of input beams and the plurality of output beams correspond toa plurality of user beams and a plurality of gateway beams by which aplurality of gateway terminals service a plurality of user terminals;and the robust beam group switching pattern is configured to maintain atleast a predefined amount of capacity across the plurality of user beamswith up to a certain extent of degradation in capacity of the pluralityof gateways.
 30. The satellite of claim 2, wherein: the non-robust beamgroup switching pattern and the robust beam group switching pattern aretwo of a plurality of beam group switching patterns; and the satellitecomprises a plurality of beam group switching subsystems, eachconfigured to selectively couple any one of an associated plurality ofthe input subsystems with any respective one of an associated pluralityof the output subsystems according to an associated one or more of theplurality of beam group switching patterns.
 30. A method for beam groupswitching in a satellite communications system, the method comprising:receiving communications by input subsystems of a satellite via aplurality of input beams; routing the communications from the inputsubsystems to output subsystems of the satellite via a beam groupswitching subsystem configured, in each of a plurality of time slots, toselectively couple any one of the input subsystems with any respectiveone of the output subsystems, the routing comprising: configuring thebeam group switching subsystem, for first time slots of a first frame,to couple each one of the output subsystems with a corresponding one ofthe input subsystems according to a non-robust beam group switchingpattern; and configuring the beam group switching subsystem, for secondtime slots of a second frame, to couple at least one of the outputsubsystems sequentially with two or more of the input subsystemsaccording to a robust beam group switching pattern; and transmitting thecommunications from the output subsystems via a plurality of outputbeams.
 31. The method of claim 30, wherein: in one of the plurality oftime slots, the receiving comprises receiving forward-linkcommunications by at least one of the input subsystems via at least oneof the plurality of input beams from at least one of a plurality ofgateway terminals, and the transmitting comprises transmitting theforward-link communications by at least one of the output subsystems viaat least one of the plurality of output beams to at least some of aplurality of user terminals; and in another of the plurality of timeslots, the receiving comprises receiving return-link communications byat least one of the input subsystems via at least one of the pluralityof input beams from the at least some of the plurality of userterminals, and the transmitting comprises transmitting the return-linkcommunications by at least one of the output subsystems via at least oneof the plurality of output beams to the at least one of the plurality ofgateway terminals.
 32. The method of claim 30, wherein: each beam groupof a plurality of beam groups comprises a respective subset of theplurality of input beams and a respective subset of the plurality ofoutput beams; and each beam group is associated with a respective one ofthe input subsystems and a respective one of the output subsystems, suchthat, for each beam group, the respective one of the input subsystems isto receive communications via the respective subset of the plurality ofinput beams of the beam group, and the respective one of the outputsubsystems is to transmit communications via the respective subset ofthe plurality of output beams of the beam group.
 33. The method of claim32, wherein: the plurality of input beams and the plurality of outputbeams correspond to user beams and gateway beams, such that each userbeam comprises a respective one of the input beams and a respective oneof the output beams that enable communications with a respective set ofuser terminals, and each gateway beam comprises a respective one of theinput beams and a respective one of the output beams that enablecommunications with at least a respective gateway terminal; and eachbeam group comprises a gateway beam and a plurality of user beams. 34.The method of claim 33, wherein: a first beam group of the plurality ofbeam groups is associated with a first of the output subsystems and witha first of the two or more of the input subsystems, the first beam grouphaving a first gateway beam and a first plurality of user beams; asecond beam group of the plurality of beam groups is associated with asecond of the output subsystems and with a second of the two or more ofthe input subsystems, the second beam group having a second gateway beamand a second plurality of user beams; the configuring the beam groupswitching subsystem comprises: for each of the first time slots,coupling the first gateway beam with one of the first plurality of userbeams according to the non-robust beam group switching pattern; for atleast one of the second time slots, coupling the first gateway beam withone of the first plurality of user beams according to the robust beamgroup switching pattern; and for at least another of the second timeslots, coupling the second gateway beam with one of the first pluralityof user beams according to the robust beam group switching pattern. 35.The method of claim 30, wherein the routing further comprises:selecting, by each of the input subsystems, a respective one of theplurality of input beams according to a first input/output (I/O)switching pattern and according to a second I/O switching pattern forthe for each of the first time slots and the second time slots,respectively; and selecting, by each of the output subsystems, arespective one of the plurality of output beams according to the firstI/O switching pattern and according to a second I/O switching patternfor the for each of the first time slots and the second time slots,respectively, such that: for each of the first time slots, each of aselected subset of the input beams is coupled with a respective one of aselected subset of the output beams, according to the first I/Oswitching pattern and the non-robust beam group switching pattern; andfor each of the second time slots, each of a selected subset of theinput beams is coupled with a respective one of a selected subset of theoutput beams, according to the second I/O switching pattern and therobust beam group switching pattern in each of the second time slots.36. The method of claim 30, further comprising: detecting an outage ofat least one of a plurality of gateway terminals in communication withthe satellite, wherein: the configuring the beam group switchingsubsystem for the first time slots is prior to the detecting, and theconfiguring the beam group switching subsystem for the second time slotsis in response to the detecting.
 37. The method of claim 30, wherein theconfiguring the beam group switching subsystem, for the second timeslots, comprises receiving the robust beam group switching pattern bythe satellite via a ground segment component.
 38. The method of claim30, wherein the configuring the beam group switching subsystem, for thesecond time slots, comprises retrieving the robust beam group switchingpattern from on-board storage of the satellite having, stored thereon, aset of alternate beam group switching patterns.
 39. The method of claim30, further comprising: detecting an outage of at least one of aplurality of gateway terminals in communication with the satellite; andselecting the robust beam group switching pattern in accordance with thedetecting, the robust beam group switching pattern being one of a set ofalternate beam group switching patterns previously stored at thesatellite, each associated with outage of a corresponding one of theplurality of gateway terminals.